The following costs result from the production and sale of 4,200 drum sets manufactured by Tight Drums Company for the year ended December 31, 2015. The drum sets sell for $270 each. The company has a 25% income tax rate.

Variable production costs
Plastic for casing	$	88,200
Wages of assembly workers		361,200
Drum stands		126,000
Variable selling costs
Sales commissions		79,800
Fixed manufacturing costs
Taxes on factory		12,000
Factory maintenance		24,000
Factory machinery depreciation		84,000
Fixed selling and administrative costs
Lease of equipment for sales staff		24,000
Accounting staff salaries		74,000
Administrative management salaries		154,000
Compute its contribution margin per unit and its contribution margin ratio.